Unit of Force, Force Units | Physics@TutorVista.com Top Unit of force The development of the metric system is a basic state of the currently used accepted unit system that is the International System of Units. This idea was first given by German mathematician Gauss. He combined metric units with the French unit system to form a complete system of unit for mechanics. After then it was extended for electricity and magnetism. The International System of Units gives the SI model system. It includes seven dimensionally independent basic units and a various derived units which are derived from seven fundamental units. There are also other unit systems like FPS system, CGS system, MKS system etc. Here, we will discuss the units of force in various systems of units. We know that force is the effect which changes the position of the object. It is mainly influenced with the mass and acceleration of the object. Let’s discuss about the measured unit of force. Sir Isaac Newton has established the following formula relating to the mass and acceleration of an object when it is subjected to a force. The formula is, F = ma m is the mass of the object a is the acceleration it acquires when subjected to force F Like any other quantity, force also has an unit.

The magnitude of a force can be used in different types of units based on different systems of measurements. Before we go into those details, let us do the fundamental dimensional analysis to find what basic unit is used to measure force. As per definition, force, F = ma. Therefore, the unit of force must contain the basic physical dimensions. That is, Basic unit of force = $\frac{(Mass \times Distance)}{(Time^{2})}$ = MLT -2Thus, the dimensional formula for Force is [MLT -2]. Force Units The basic unit of force in terms of physical dimensions is MLT -2. In practical sense, we refer to the weight of an object rather than its mass. Hence, we can rewrite the basic unit of force as, F = (W/g)LT-2 W is the weight of the object g is the acceleration due to gravity Thus, the unit of forces are classified into two systems called absolute system and gravitational system. The measurement of forces in absolute system are not dependent on gravitational force whereas, measurement of forces in gravitational system are dependent on gravitational forces. Hence, the measures of forces in gravitational system differ on other planets compared to earth.

It may be easily identified that,the unit in gravitational system = unit in absolute system $times $ acceleration due to gravity. Basically, we can express the Unit of Measurement of Force in following ways : FPS unit of force Now, let us go into the details of various units of measurement of force. FPS Unit of Force Back to Top When a mass of 1 pound is subjected to an acceleration of 1 ft/sec2, the force applied is called 1poundal. The unit is abbreviated as pdl. One poundal is 1lbm-ft/sec2. A pound force is defined as the gravitational force exerted on 1 pound mass. It is denoted as lbf. When we say that the weight of the person is 150 pounds, we actually mean 150 lbf. Poundal and pound force are the units of measurement of forces in fps system. Metric Unit of Force Back to Top In metric system 1 kilogram force is the gravitational force exerted on 1 kilogram weight. It is similar to pound force in fps system. It is denoted as kgf. The force that produces 1 m/sec2 acceleration on 1 kilogram mass is called as 1 Newton.

This is named in the honor of Sir Isaac Newton. In short it is abbreviated as N. The metric unit of force has also smaller measures and that system is called cgs system. In cgs system, a force is measured in terms of dynes. A force of 1 dyne produces an acceleration of 1cm/sec2 on a mass of 1 gram. The gravitational force exerted on 1 gram weight is called gram force and denoted as gf. SI Unit of Force Back to Top Internationally, the traders, engineers and scientists had jointly decided to use a single system of unit which is called as SI units. It is a short form of Standard International. In SI units, Newton is the unit recognized for measurement of force. Relationship between newton and dyne One newton is the force that produces an acceleration of 1m/s2 in a body of mass 1kg. 1 newton = 1 kg x 1m/s2 Another such unit for force in the CGS system, is the dyne. One dyne is the force which produces an acceleration of 1cm/s2 in a body of mass 1gram.

1 dyne = 1 gm x 1cm/s2 The relation between one dyne and one Newton is, 1 N = 105 dyne Back to Top As defined already, the force that produces 1 m/sec2 acceleration on 1 kilogram mass is called as 1 Newton. This unit is recognized as SI unit. Since, forces are also measured in other types of units, a necessity arises to express all such units in equivalent to Newton unit of force. The following table describes such conversions. Unit Units of Force by Ron Kurtus - Physics Lessons: School for Champions Units of Force by Ron Kurtus (revised 1 October 2015) A force is a push, pull, or dragging on an object that changes its velocity or direction. A unit of force is an arbitrary measurement that we designate as "1" (unit), so that all other measurements of force are multiples of that unit. Most often, force is designated as a newton (N) in the metric or SI system of measurement. The newton has applications in various scientific measurements. There are other units, not used as often. Questions you may have include: What is the definition of the newton?

What are some applications of the newton? what are other units of force? This lesson will answer those questions. Useful tool: Units Conversion Definition of newton A newton is the force required to give a mass of 1 kilogram (1 kg) an acceleration of 1 meter per second per second (1 m/s2). It is abbreviated as N. This unit of measurement is in the metric or SI system and is used in scientific work more than other units of force. 1 N is equivalent to 1 kg-m/s2. Applications of the newton The newton combined with other measurements is used in various applications. Moment of force The unit of torque or moment of force is the newton-meter (N-m), where m is the moment arm. Energy, work and heat The newton-meter (N-m) is also the definition of the joule (J), which is a unit of energy. It can be seen that the units of kinetic energy E = ½mv2 are in kilogram-meter2/seconds2 and kg-m2/s2 = N-m. Power and radiant flux Power is energy per second or N-m/s, with the unit of watt. This is also the unit for radiant flux or power from electromagnetic radiation.

Pressure The unit of pressure is the pascal (P), which is the force per unit area (N-m2). Other units of force There are other units of force, not as commonly used as the newton. Dyne A dyne is the force required to give a mass of 1 gram (1 g) an acceleration of 1 centimeter per second per second (1 cm/s2). 1 N = 100,000 dynes. You might use the dyne, if working with small objects. Poundal and pound A poundal is the force required to give a mass of 1 pound (1 lb) an acceleration of 1 foot per second per second (1 ft/s2). 1 poundal equals 0.1382 newtons. A pound is the force applied on a mass of 1 pound (1 lb) by the acceleration due to gravity. It is a non-technical unit of force and is also called the weight. These units of force are in the English system and are seldom used in scientific measurements. Summary A force acts on an object to change its velocity or direction.

In most scientific work, force is designated as a newton (N) in the metric or SI system of measurement. The newton has applications in various scientific measurements. There are other units, not used as often. Be forceful in your actions Resources and references The Meaning of Force Newton's Laws - Lesson 2 - Force and Its Representation The Meaning of Force Determining the Net Force A force is a push or pull upon an object resulting from the object's interaction with another object. Whenever there is an interaction between two objects, there is a force upon each of the objects. When the interaction ceases, the two objects no longer experience the force. Forces only exist as a result of an interaction. For simplicity sake, all forces (interactions) between objects can be placed into two broad categories: contact forces, and forces resulting from action-at-a-distance Contact forces are those types of forces that result when the two interacting objects are perceived to be physically contacting each other. Examples of contact forces include frictional forces, tensional forces, normal forces, air resistance forces, and applied forces. These specific forces will be discussed in more detail later in Lesson 2 as well as in other lessons.

Action-at-a-distance forces are those types of forces that result even when the two interacting objects are not in physical contact with each other, yet are able to exert a push or pull despite their physical separation. Examples of action-at-a-distance forces include gravitational forces. For example, the sun and planets exert a gravitational pull on each other despite their large spatial separation. Even when your feet leave the earth and you are no longer in physical contact with the earth, there is a gravitational pull between you and the Earth. Electric forces are action-at-a-distance forces. For example, the protons in the nucleus of an atom and the electrons outside the nucleus experience an electrical pull towards each other despite their small spatial separation. And magnetic forces are action-at-a-distance forces. For example, two magnets can exert a magnetic pull on each other even when separated by a distance of a few centimeters. These specific forces will be discussed in more detail later in Lesson 2 as well as in other lessons. Examples of contact and action-at-distance forces are listed in the table below. Contact Forces The Newton Force is a quantity that is measured using the standard metric unit known as the Newton.

A Newton is abbreviated by an "N." To say "10.0 N" means 10.0 Newton of force. One Newton is the amount of force required to give a 1-kg mass an acceleration of 1 m/s/s. Thus, the following unit equivalency can be stated: 1 Newton = 1 kg • m/s2 Force is a Vector Quantity A force is a vector quantity. As learned in an earlier unit , a vector quantity is a quantity that has both magnitude and direction. To fully describe the force acting upon an object, you must describe both the magnitude (size or numerical value) and the direction. Thus, 10 Newton is not a full description of the force acting upon an object. In contrast, 10 Newton, downward is a complete description of the force acting upon an object; both the magnitude (10 Newton) and the direction (downward) are given. Because a force is a vector that has a direction, it is common to represent forces using diagrams in which a force is represented by an arrow. Such vector diagrams were introduced in an earlier unit and are used throughout the study of physics.

The size of the arrow is reflective of the magnitude of the force and the direction of the arrow reveals the direction that the force is acting. (Such diagrams are known as free-body diagrams and are discussed later in this lesson .) Furthermore, because forces are vectors, the effect of an individual force upon an object is often canceled by the effect of another force. For example, the effect of a 20-Newton upward force acting upon a book is canceled by the effect of a 20-Newton downward force acting upon the book. In such instances, it is said that the two individual forces balance each other; there would be no unbalanced force acting upon the book. Other situations could be imagined in which two of the individual vector forces cancel each other ("balance"), yet a third individual force exists that is not balanced by another force. For example, imagine a book sliding across the rough surface of a table from left to right. The downward force of gravity and the upward force of the table supporting the book act in opposite directions and thus balance each other. However, the force of friction acts leftwards, and there is no rightward force to balance it. In this case, an unbalanced force acts upon the book to change its state of motion .

The exact details of drawing free-body diagrams are discussed later . For now, the emphasis is upon the fact that a force is a vector quantity that has a direction. The importance of this fact will become clear as we analyze the individual forces acting upon an object later in this lesson . Units: The International System Using the Dictionary The International System of Units (SI) All systems of weights and measures, metric and non-metric, are linked through a network of international agreements supporting the International System of Units. The International System is called the SI, using the first two initials of its French name Système International d'Unités. The key agreement is the Treaty of the Meter (Convention du Mètre), signed in Paris on May 20, 1875. 48 nations have now signed this treaty, including all the major industrialized countries. The United States is a charter member of this metric club, having signed the original document back in 1875.

The SI is maintained by a small agency in Paris, the International Bureau of Weights and Measures (BIPM, for Bureau International des Poids et Mesures), and it is updated every few years by an international conference, the General Conference on Weights and Measures (CGPM, for Conférence Générale des Poids et Mesures), attended by representatives of all the industrial countries and international scientific and engineering organizations. The 24th CGPM met in 2011; the next meeting will be in 2014. As BIPM states on its web site, "The SI is not static but evolves to match the world's increasingly demanding requirements for measurement." At the heart of the SI is a short list of base units defined in an absolute way without referring to any other units. The base units are consistent with the part of the metric system called the MKS system . In all there are seven SI base units: the meter for distance, the mole for amount of substance, and the candela for intensity of light. Other SI units, called SI derived units , are defined algebraically in terms of these fundamental units.

For example, the SI unit of force, the newton , is defined to be the force that accelerates a mass of one kilogram at the rate of one meter per second per second. This means the newton is equal to one kilogram meter per second squared, so the algebraic relationship is N = kg·m·s-2. Currently there are 22 SI derived units that have special names and symbols.

They include: the radian and steradian for plane and solid angles, respectively; the newton for force and the pascal for pressure; the joule for energy and the watt for power; the degree Celsius for everyday measurement of temperature; units for measurement of electricity: the coulomb (charge), volt (potential), farad (capacitance), ohm (resistance), and siemens (conductance); units for measurement of magnetism: the weber (flux), tesla (flux density), and henry (inductance); the lumen for flux of light and the lux for illuminance; the hertz for frequency of regular events and the becquerel for rates of radioactivity and other random events; the gray and sievert for radiation dose; and the katal , a unit of catalytic activity used in biochemistry. Future meetings of the CGPM may make additions to this list; the katal was added by the 21st CGPM in 1999.

In addition to the 29 base and derived units, the SI permits the use of certain additional units, including: the traditional mathematical units for measuring angles ( degree , arcminute, and arcsecond ); the traditional units of civil time ( minute , hour , day , and year ); two metric units commonly used in ordinary life: the liter for volume and the tonne (metric ton) for large masses; the logarithmic units bel and neper (and their multiples, such as the decibel ); and three non-metric scientific units whose values represent important physical constants: the astronomical unit , the atomic mass unit or dalton , and the electronvolt . The SI currently accepts the use of certain other metric and non-metric units traditional in various fields. These units are supposed to be "defined in relation to the SI in every document in which they are used," and "their use is not encouraged." These barely-tolerated units might well be prohibited by future meetings of the CGPM.

They include: the nautical mile and knot , units traditionally used at sea and in meteorology; the are and hectare , common metric units of area; the bar , a pressure unit, and its commonly-used multiples such as the millibar in meteorology and the kilobar in engineering; the angstrom and the barn , units used in physics and astronomy. The SI does not allow use of any units other than those listed above and their multiples. In particular, it does not allow use of any of the English traditional units (the horsepower, for example), nor does it allow the use of any of the algebraically-derived units of the former CGS system , such as the erg, gauss, poise, stokes, or gal. In addition, the SI does not allow use of other traditional scientific and engineering units, such as the torr, curie, calorie, or rem. Certain scientific fields have defined units more or less compatible with the SI, but not part of the SI. The use of the jansky in astronomy is a good example. There is always the chance that future meetings of the CGPM could add these units to the SI, but for the present they are not approved.

For multiples of approved units, the SI includes a list of prefixes . This list has been extended several times, most recently by the 19th CGPM in 1991. Prefixes now range from yotta- at 1024 (one septillion) to yocto- at 10-24 (one septillionth). There seems to be some need for another extension, but this question has not been addressed at recent CGPM's. The SI does not allow these prefixes to be used for binary multiples, such as the use of "kilobit" to mean 1024 bits instead of 1000. For binary multiples a new list of special prefixes has been established by the International Electrotechnical Commission. Each SI unit is represented by a symbol, not an abbreviation. The use of unit symbols is regulated by precise rules . These symbols are the same in every language of the world. However, the names of the units themselves vary in spelling according to national conventions. Therefore, it is correct for Americans to write meter and Germans to write Meter, and it is also correct for the British to write metre, Italians to write metro, and Poles to write metr.

See Spelling of Metric Units for additional comments. Return to the Dictionary Contents page . You are welcome to email the author (rowlett@email.unc.edu) with comments and suggestions. All material in this folder is copyright 2012 by Russ Rowlett and the University of North Carolina at Chapel Hill. Permission is granted for personal use and for use by individual teachers in conducting their own classes. All other rights reserved. You are welcome to make links to this page, but please do not copy the contents of any page in this folder to another site. The material at this site will be updated from time to time. Posted July 2000; last revised December 4, 2008. Force | Units of Measurement Wiki | Fandom powered by Wikia Edit Force in its most primitive definition can be thought of as that which when acting alone causes an object to accelerate. In a practical sense forces can be divided into two groups: contact forces and field forces. Contact forces require the physical contact of one object with other such as a hammer striking a nail or the force exerted by a gas under pressure--gas produced by exploding gunpowder forces a heavy ball out of a cannon.

Field forces on the other hand need no physical medium of contact. Gravity and magnetism are examples of such forces. It should be noted however, that fundamentally all forces are in fact field forces. The force of hammer striking the nail in the previous example turns out to be a clash of the electric forces in both hammer and nail. Nevertheless it is appropriate in some cases to maintain these two classifications for ease of understanding. Quantitative definition Edit In a simple point-like system, one in which objects have no dimensions and cannot rotate or deform, the only change the system can experience is a change of its movement (more precisely of its center of mass ); that is, its speed , or more generally its momentum . Since the rise of the atomic theory , any physical system has been considered in classical physics as composed of point-like systems called atoms or molecules . Therefore, all forces can be defined by their effect ; that is, by the change of movement they induce on point-like systems. This change of movement can be quantified by the acceleration (the derivative of velocity ), but a given force will induce different effects on different point-like systems depending on the system.

The discovery by Isaac Newton that a given force will induce an acceleration in inverse proportion to a quantity called the mass of inertia or inertial mass which is independent of the speed of the system is Newton's second law . This law allows us to predict the effect of a force on any point-like system whose mass is known. It is usually written as: F = dp/dt = d(m·v)/dt = m·a (in the case where m does not depend on t) where v is the velocity , m is the mass , and a=d²x/dt² is the acceleration, the second derivative with respect to t of the position vector x. If the mass m is measured in kilograms and the acceleration a is measured in meters per second squared , then the unit of force is kilogram x meter/second squared. This unit is called the newton : 1 N = 1 kg x 1 m/s². This equation is a system of three second-order differential equations with respect to the three- dimensional position vector which is an unknown function of time. This equation can be solved if F is a known function of x and some of its derivatives and if the mass m is known.

Morevover the boundary conditions are required; for example, the values of the position vector and x and the velocity v at the starting time, say t=0. Of course, this formula is only useful if one knows the numerical values of F and m. The definition above is an implicit definition, arrived at as follows. One defines a reference system (one litre of water ) and a reference force (the gravitational force applied by the Earth on it at the altitude of Paris ). One takes Newton's second law for granted (one postulates that it is true) and measures the acceleration induced by the reference force on the reference system. This gives us a mass unit (1 kg) and a force unit (the older unit of 1 kilogram-force = 9.81 N). Once this is done, one can measure any force by the acceleration it induces on the reference system and measure the inertial mass of any system by measuring the acceleration induced on this system by the reference force. Force is often considered a fundamental quantity in physics, but there are more fundamental quantities, such as momentum (p = mass m x velocity v).

Energy, measured in joules , is still less fundamental than force and momentum, because it is defined as work, and work is defined in terms of force. The two most fundamental theories of nature - quantum electrodynamics and general relativity - do not contain the concept of force at all. Although not the most fundamental quantity in physics, force is an important basic mathematical concept from which other concepts, such work and pressure (measured in pascals ), are derived. Force is sometimes confused with stress . Types of force The four fundamental forces describe every observable phenomenon including the many other forces observed such as: Coulomb's force (the force between electrical charges ), gravitational force (force between masses ), magnetic force , frictional forces, centripetal , centrifugal , impact force , and spring force , to name a few. Forces can also be classified into conservative forces and nonconservative forces. Conservative forces are equivalent to the gradient of a potential , and include gravity , electromagnetic force, and spring force. Nonconservative forces include friction and drag . Properties of force Edit Because momentum is a vector, then force, being its time derivative, is also a vector - it has magnitude and direction . Forces can be added together using the parallelogram of force .

When two forces act on an object, the resulting force, the resultant, is the vector sum of the original forces. This is called the principle of superposition . The magnitude of the resultant varies from zero to the sum of the magnitudes of the two forces, depending on the angle between their lines of action. If the two forces are equal, but opposite, the resultant is zero. This condition is called static equilibrium , with the result that the object remains at rest or moves with a constant velocity. As well as being added, forces can be can also be broken down (or 'resolved'). For example, a horizontal force pointing northeast can be split into two forces, one pointing north, and one pointing east. Summing these component forces using vector addition yields the original force. Force vectors can also be three-dimensional, with the third (vertical) component at right-angles to the two horizontal components.

Forces in theory The total ( Newtonian ) force, in newtons , on an object at any given time is defined as the rate of change of the object's velocity multiplied by the object's mass : where vo is its initial velocity (measured in meters per second ) v is its final velocity (measured in meters per second) T is the time from the initial state to the final state (measured in seconds ); Lim T→0 is the limit as T tends towards zero. Force was so defined to explain the effects of superimposing situations: if in one situation, a force is experienced by a particle, and if in another situation another force is experienced by that particle, then in a third situation, which (according to standard physical practice) is taken to be a combination of the two individual situations, the force experienced by the particle will be the vector sum of the individual forces experienced in the first two situations. This superposition of forces, and the definition of inertial frames and inertial mass , are the empirical content of Newton's laws of motion . There are other ways to look at the above definition of force.

First, the mass of a body multiplied by its velocity is called its momentum, p, so the above definition is equivalent to: If F is not constant over Δt, then this is the definition of average force over the time interval. To apply it at an instant we apply an idea from calculus . If we graph p as a function of time, the average force will be the slope of the line connecting the momentum at two times. Taking the limit as the two times get closer together gives the slope at an instant, which is called the derivative: Many forces are associated with a potential energy field. For instance, the gravitational force acting upon a body can be seen as the action of the gravitational field that is present at the body's location. The potential field is defined as that field whose gradient is equal and opposite to the force produced at every point: The derivative of force with respect to time is called yank . Higher order derivatives are sometimes used, but they lack names because of their rarity. In most explanations of mechanics , force is usually defined only implicitly, in terms of the equations that work with it.

Some physicists, philosophers and mathematicians, such as Ernst Mach , Clifford Truesdell and Walter Noll , have found this problematic and sought a more explicit definition of force. Units of measurement The SI unit used to measure force is the [[newton}} (symbol N), which is equivalent to kg·m·s−2. Non-SI units of force and mass Edit The F=m·a relationship can be used with any consistent units ( SI or CGS ). If these units are not consistent, a more general form, F=k·m·a, can be used, where the constant k is a conversion factor dependent upon the units being used. For example, in imperial engineering units, F is measured in " pounds force " or "lbf", m in "pounds mass" or "lb", and a in feet per second squared. In this particular system, one needs to use the more general form above, usually written F=m·a/gc with the constant normally used for this purpose gc = 32.174 lb·ft/(lbf·s2) equal to the reciprocal of the k above.

As with the kilogram, the pound is colloquially used as both a unit of mass and a unit of force. 1 lbf is the force required to accelerate 1 lb at 32.174 ft per second squared, since 32.174 ft per second squared is the standard acceleration due to terrestrial gravity. Another imperial unit of mass is the slug, defined as 32.174 lb. It is the mass that accelerates by one foot per second squared when a force of one lbf is exerted on it. When the standard gee (an acceleration of 9.80665 m/s²) is used to define pounds force, the mass in pounds is numerically equal to the weight in pounds force. However, even at sea level on Earth, the actual acceleration of free fall is quite variable, over 0.53% more at the poles than at the equator.

Thus, a mass of 1.0000 lb at sea level at the equator exerts a force due to gravity of 0.9973 lbf, whereas a mass of 1.000 lb at sea level at the poles exerts a force due to gravity of 1.0026 lbf. The normal average sea level acceleration on Earth (World Gravity Formula 1980) is 9.79764 m/s², so on average at sea level on Earth, 1.0000 lb will exerts a force of 0.9991 lbf. The equivalence 1 lb = 0.453 592 37 kg is always true, by definition, anywhere in the universe. If you use the standard gee which is official for defining kilograms force to define pounds force as well, then the same relationship will hold between pounds-force and kilograms-force (an old non-SI unit is still used). If a different value is used to define pounds force, then the relationship to kilograms force will be slightly different—but in any case, that relationship is also a constant anywhere in the universe.

What is not constant throughout the universe is the amount of force in terms of pounds-force (or any other force units) which 1 lb will exert due to gravity. By analogy with the slug, there is a rarely used unit of mass called the "metric slug". This is the mass that accelerates at one meter per second squared when pushed by a force of one kgf . An item with a mass of 10 kg has a mass of 1.01972661 metric slugs (= 10 kg divided by 9.80665 kg per metric slug). This unit is also known by various other names such as the hyl , TME (from a German acronym), and mug (from metric slug). Another unit of force called the poundal (pdl) is defined as the force that accelerates 1 lbm at 1 foot per second squared. Given that 1 lbf = 32.174 lb times one foot per second squared, we have 1 lbf = 32.174 pdl.

In conclusion, we have the following conversions: 1 kgf (kilopond kp) = 9.80665 newtons 1 metric slug = 9.80665 kg 1 lbf = 32.174 poundals 1 slug = 32.174 lb 1 kgf = 2.2046 lbf The kilogram-force is a unit of force that was used in various fields of science and technology. In 1901, the CGPM improved the definition of the kilogram-force, adopting a standard acceleration of gravity for the purpose, and making the kilogram-force equal to the force exerted by a mass of 1 kg when accelerated by 9.80665 m/s².

The kilogram-force is not a part of the modern SI system, but is still used in applications such as: Thrust of jet and rocket engines Spoke tension of bicycles Draw weight of bows Torque wrenches in units such as "meter kilograms" or "kilogram centimeters" (the kilograms are rarely identified as units of force) Engine torque output (kgf·m expressed in various word orders, spellings, and symbols) Pressure gauges in "kg/cm²" or "kgf/cm²" In colloquial, non-scientific usage, the "kilograms" used for "weight" are almost always the proper SI units for this purpose. They are units of mass, not units of force. The symbol "kgm" for kilograms is also sometimes encountered. This might occasionally be an attempt to disintinguish kilograms as units of mass from the "kgf" symbol for the units of force. It might also be used as a symbol for those obsolete torque units (kilogram-force meters) mentioned above, used without properly separating the units for kilogram and meter with either a space or a centered dot.

Forces in everyday life Forces are part of everyday life, with examples such as: gravity : objects fall, even after being thrown upwards, or slide and roll down friction : floors and objects are not extremely slippery Physical quantities and SI units Physical quantities and SI units Physical quantities and SI units Physical quantities have a numerical value (a number) and a unit of measurement (e.g. two kilograms, one metre, ten newtons). In "2 kilograms of bananas", "2" is the numerical value and "kilograms" is the unit. A is a specific magnitude of a physical quantity that has been adopted by convention. Kilogram, degree Celsius and centimetre are different units. The , abbreviated as SI (in French), defines the set of units of measurement and their symbols that are most widely used by scientists. The metre is the SI unit for distance. The kelvin is the SI unit for temperature. The mass of some strawberries is measured. They have a mass of $$146 \text{ g}.$$ There are seven SI base units in the International System of Units. They can be used to define all other SI units (the derived units). The seven SI base units Quantity SI derived units are products and/or ratios of base units.

Speed is the change in distance per unit of time. The unit of speed is the unit of distance (same as length) divided by the unit of time ($$\text{m/s}$$). Some derived units have special SI names and symbols. Force is assigned the SI unit newton $$(\text{N})$$, where $$1\text{ N}=1\text{ kg m s}^{-2}$$. The symbols for the SI units are written in uppercase if they are named after a person (like Isaac Newton). Otherwise they are always written in lowercase (as in the metre). $$$\text{Length} = 1 \um \quad \text{Force} = 10 \text{ N}$$$ Unit prefixes Unit prefixes are symbols placed before the symbol of a unit to specify the order of magnitude of a quantity. They make it easier to express very large or very small quantities. "k" (kilo) is the unit prefix in the unit "kg" (kilogram). A unit prefix stands for a specific positive or negative power of 10. "k" stands for $$1000 = 10^{3}$$. The kilogram is the only SI base unit that contains a prefix.

Additional prefixes (e.g. millikilograms) are not allowed. Prefix Table labelling conventions In a table, it is conventional to have the independent variable (the variable being controlled in an experiment) in the first column from the left. The dependent variables (i.e. the variable(s) that are being observed or calculated depending on the independent variable) in the columns are reported on the right. A student passes different values of electrical current through a resistor. For each value of current, he records the voltage across the resistor. The independent variable is the current and the dependent variable is the voltage. The headings of the table are ideally represented as:$$$\frac{\text{name of quantity, symbol}}{\text{unit}}$$$ A typical table of experimental measurements is given below: $$$\frac{\text{Time, }t}{s}$$$ $$$\frac{\text{Speed, }v}{\text{m/s}}$$$ $$10$$ In a graph, it is conventional to have the independent variable on the horizontal axis and the dependent variable as the vertical axis. The axis labels are represented, ideally, in the same manner as table headings.

The axis labels are ideally represented as:$$$\frac{\text{name of quantity, symbol}}{\text{unit}}$$$ In most cases, the name of the quantity is omitted from the axis labels (it is assumed that the reader understands the symbol). Graph labelling conventions. The independent variable (time) is on x-axis while the dependent variable (speed) is on the y-axis. Estimation of common physical quantities Estimation involves finding a value that is reasonably close to the true value of a physical quantity without any measurement. It is used to check any measured or reported values. If you know that the mass of an adult is about $$70\text{ kg}$$, you can estimate that the mass of a bag of apples must be less than $$70\text{ kg}$$. Some values of common physical quantities are as follows: Physical quantity Units in Physics (mechanical, electricity, magnetism, light and optics) including Si units. | Anthology of Ideas Units in Physics (mechanical, electricity, magnetism, light and optics) including Si units. Posted on by aaron + This is a reference list with notes of all SI and derived units in physics.

The notes provide a brief explanation of some of the more confusing elements, but be warned that the full explanation could take many pages, and may be explained elsewhere on this website. Physics has only 5 base units.

(Plus the SI units Mole and Candela, but these are rarely used in Physics.) Name Meter (m) A meter is defined as the distance light travels in a vacumm in of a second (in physics it is customary to use metric measurements although the basic principles apply if you to use feet instead of meters) Mass m, M (when used with measurements in meters) Kilogram (kg) A kilogram is defined as the weight of a specific platinum-iridium cylinder Time Seconds are defined as 9,192,631,770 vibrations of radiation from a cesium atom Temparature A degree kelvin is defined as of the distance between absolute 0 and the triple point of water Electric Current I Ampere (A) An ampere is the amount of charge (C) passing through a surface per second, and is defined as the current which produces a force of newtons per meter of length between two infinitely long, perfectly straight and parallel conductors with an infinitely small cross section separated by one meter in a vacuum.. Each of these base units is defined on fundamental constants, and all other units are based on these five units.

At times it useful to break longer equations down to their most basic units to determine if the equation makes sense. The most common combinations of these basic units are given their own symbols and names. These common units are as follows. Name (alphabetically) a (meters per second squared) Acceleration is literally the rate of change of the rate of change of an object’s position. Angle , radian A radian is defined as the angle an arc length, equal to the circle’s radius, makes with the center of the circle. Capacitance Q ), q ,e (of elementary particles) Coulomb (C) Literally the charge is the amount of current that flows over the entire time period. Density Density is the amount of mass in every cubed unit length Displacement s, d (distance), h (height) meters – m Displacement is the total change in length in any single direction. Sometimes it is used as the absolute change in distance –if you were walk all the way around the earth less one meter, your displacement would be one meter Electric Field An electric field is the amount of electric potential over any given area. Electric Flux Electric flux is the electric field through some area.

Electromotive Force (emf) Electromotive force is a potential difference in volts. Electron Volt eV The Electron Volt is the amount of energy change of a charge-field system when a charge of magnitude e is moved through a potential difference of 1V. It is used in place of the Joule (energy). Energy Q Joule (J) Joule is used for work, heat and energy, but remember that Joule is a unit of energy not of energy transfer. This means that heat can have a Joule of energy, but can’t be measured in Newtons. Magnetic Field Potential is the amount of excess charge. It can be compared with potential energy. Power Power is the amount of work done in any given time. Pressure R Ohm Resistance is the amount of energy that is lost in the transfer of energy through an object. Torque Torque is usually shown with units N*m even though it is technically joules. Velocity Velocity is the speed and direction of an object. Wavelength Joule (J) Work is the amount of force outputted over some distance. For of the derived units such as electric flux there are multiple possible unit definitions.

The two standard definitions for electric flux are and as the following derivation from the former to the latter shows they are both correct. This derivation only used units given in the above table, but there are other ways. Categorized as: Tweet Holbrook chick you need more about the units used for the formulas such as what units mass can be in ect,it would be very helpful!!!!! —-Thanks—- can you tell me please what is the SI unit of stress? archana unit of stress is NEWTON PER METER SQAURE sameer khan the unit of stress if pascal and newton per meter sqared both .. the unit of magnetic field strength is ampere per meter and physical units dont any any strength mohamed sulaiman can you please tell / explain to me about physics unit called victor the formula application and how it could be drived zulaikha the si unit of stree is mega pascal ksudhakar IS IT POSSIBLE TO LEARN ALL THE DIMENSIONS AND UNITS AT THE AGE OF 8YEARS HOSLAMA BEN LARDEN ROW ROW FIGHT DA POWER kashif i like these unit.

it is very helpful i am very thank ful to all subhajit yes itsnot impossible at all !! jamesavery its not really well xplained…. not so clear it really works to me thanks a lot!! more power and goDblESS

Question: In physics, what is the S I unit of force?
Answer: Newton